Method for making nano- and micro-particles for use as a proppant and fluid-loss-control additive

ABSTRACT

Nano- and micro-particles (NMP) can be formed from an oil/water emulsion. The emulsion is made by mixing a liquid solvent, at least one surfactant, a particle-forming compound, and at least curing agent. If desired, pH control agents and viscosity enhancers can be added to the liquid solvent. The particle-forming compound and the curing agents are mixed together and form the oil phase in the emulsion and after curing, the particles are formed. The nano- and micro-particles can be used as proppant to enhance the conductivity of nano- and microfractures and fluid-loss-control additive for hydraulic fracturing operations.

FIELD

The disclosure relates generally to nano- and micro-particles. Thedisclosure relates specifically to nano- and micro-particles, methodsfor making and using nano- and micro-particles as proppants andfluid-loss control additives for hydraulic fracturing operations.

BACKGROUND

Hydraulic fracturing has been an important technique to enhanceproduction of hydrocarbons from oil and gas bearing formations. In atypical hydraulic fracturing treatment, hydraulic fracturing fluidcontaining a solid proppant and a proppant-carrying liquid, such aslinear gels and slick water, is injected into the formation at apressure high enough to cause or enlarge a fracture in the reservoir.When the hydraulic fracturing fluid is removed, packed proppant can keepthe fracture open, allowing fluids to flow from the formation throughthe proppant to the production wellbore. The proppant is of extremeimportance as it provides a long-term conductivity of the fracture.

Formation damage may be caused by fracturing fluid leak-off inreservoirs during and after hydraulic fracturing operations. U.S. Publ.No. 20160355727 to R. Barati et al. discloses a method of usingnanoparticles having an average diameter of less than 1 μm, comprisingsilicon oxide, calcium oxide, aluminum oxide, and made of fly ash frompower plants as fluid loss minimizing additives. The nanoparticles aredispersed in a fracturing fluid made of 2% KCl with the addition ofcrosslinked guar, leading to the formation a uniform filter cake whichapparently reduced the fluid loss.

Nano- and micro-fractures may close after hydraulic fracturing operationbecause conventional proppants are mainly applied to keep the mainfractures open. To enhance the production of hydrocarbons, U.S. Publ.No. 20160304770 and U.S. Pat. No. 9,896,619B2 to P. Nguyen et al. usedmicroproppants including silica flour and ceramic microproppants tolargely increase the conductivity of microfractures.

Nano- and micro-particles have been applied as proppants and fluid-losscontrol additives for hydraulic fracturing operations. Nano- andmicro-proppants promote the conductivity of nano- and micro-scalefractures and minimize fluid loss thereby minimizing formation damage.It is desirable for proppants of low density to be applied to fracturingfluids; however, the prior art is deficient in means of producing nano-and micro-proppant of low density.

It would be advantageous to develop a method for producing nano- andmicro-particles of low density for use as proppants and as fluid-losscontrol additives in hydraulic fracturing operations.

SUMMARY

An embodiment of the disclosure is a method for producing a mixture ofnano- and micro-particles for use as a proppant and fluid-loss-controladditive, comprising: mixing a liquid solvent, at least one surfactant,a particle-forming compound, and at least one curing agent for about 10minutes to form an emulsion; and incubating the emulsion at about30-150° C. for about 5 to 200 minutes to permit formation of nano- andmicro-particles. In an embodiment, the emulsion is incubated at about60° C. In an embodiment, the emulsion is incubated for about 60 minutes.In an embodiment, the liquid solvent comprises water, seawater, brinecomprising monovalent, divalent, and multivalent salts, an alcoholcomprising ethanol, propanol, butanol, or combinations thereof. In anembodiment, the at least one surfactant comprises anionic surfactants,cationic surfactants, nonionic surfactants, amphoteric surfactants orcombinations thereof. In an embodiment, the particle-forming compoundcomprises aliphatic epoxides, anhydrides, glycidyl amine epoxide,cycloaliphatic epoxides, epoxy functional resins, polyurethane resins,phenol-formaldehyde resin, bis-phenol A diglycidyl ether, poly glycidylethers, acrylic resin, glycidyl ethers, bis-phenol F diglycidylethernovalac resins, or combinations thereof. In an embodiment, the atleast one curing agent comprises isophorone diamine, boron tri-fluoridederivatives, imidazolines, mercaptans, hydrazides, polyamides,functional resins, mono ethanol amine, benzyl dimethylamine, lewisacids, tertiary amines, cycloaliphatic amines, amidoamines, aliphaticamines, aromatic amines, isophorone, imidazoles, sulfide, amides ortheir derivatives. In an embodiment, the method further comprises addinga pH control agent to the emulsion. In an embodiment, the pH controlagent comprises mineral acids, sulfonic acids, carboxylic acids, sodiumhydroxide, potassium hydroxide, calcium hydroxide, or combinationsthereof. In an embodiment, the mineral acids comprise hydrochloric acid,sulfuric acid, nitric acid, or fluoroboric acid; the sulfonic acidscomprise ethanesulfonic acid or methanesulfonic acid; and the carboxylicacids comprise acetic acid. In an embodiment, the method furthercomprises adding a viscosity enhancer to the emulsion. In an embodiment,the viscosity enhancer comprises calcium carbonate nanoparticles,silicate nanoparticles, or water-soluble polymers comprisingpolyacrylamide or polyvinyl alcohol.

An embodiment of the disclosure is a nano- and micro-particle mixtureproduced from the method above. In an embodiment, the emulsion isincubated at about 60° C. and for about 60 minutes. In an embodiment,the liquid solvent comprises water, seawater, brine comprisingmonovalent, divalent, and multivalent salts, an alcohol comprisingethanol, propanol, butanol, or combinations thereof the at least onesurfactant comprises anionic surfactants, cationic surfactants, nonionicsurfactants, amphoteric surfactants or combinations thereof; theparticle-forming compound comprises aliphatic epoxides, anhydrides,glycidyl amine epoxide, cycloaliphatic epoxides, epoxy functionalresins, polyurethane resins, phenol-formaldehyde resin, bis-phenol Adiglycidyl ether, poly glycidyl ethers, acrylic resin, glycidyl ethers,bis-phenol F diglycidyl ethernovalac resins, or combinations thereof andthe at least one curing agent comprises isophorone diamine, borontri-fluoride derivatives, imidazolines, mercaptans, hydrazides,polyamides, functional resins, mono ethanol amine, benzyl dimethylamine,lewis acids, tertiary amines, cycloaliphatic amines, amidoamines,aliphatic amines, aromatic amines, isophorone, imidazoles, sulfide,amides or their derivatives. In an embodiment, the mixture furthercomprises adding a pH control agent to the emulsion; wherein the pHcontrol agent comprises mineral acids, sulfonic acids, carboxylic acids,sodium hydroxide, potassium hydroxide, calcium hydroxide, orcombinations thereof. In an embodiment, the mixture further comprisesadding a viscosity enhancer to the emulsion; wherein the viscosityenhancer comprises calcium carbonate nanoparticles, silicatenanoparticles, or water-soluble polymers comprising polyacrylamide orpolyvinyl alcohol. In an embodiment, the diameter of the nanoparticlesis less than 1 μm and the diameter of the microparticles is between 1 μmand 250 μm. In an embodiment, the density of the nanoparticles andmicroparticles is 1.50 g/ml or less.

An embodiment of the disclosure is a method of using the nano- andmicro-particles produced from the method above to increase theconductivity of microfractures and minimize fluid loss comprising addingthe particles to a pad or fracturing fluids. In an embodiment, nano-,micro-, or a mixture of nano- and micro-particles can be used.

The foregoing has outlined rather broadly the features of the presentdisclosure in order that the detailed description that follows may bebetter understood. Additional features and advantages of the disclosurewill be described hereinafter, which form the subject of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the manner in which the above-recited and otherenhancements and objects of the disclosure are obtained, a moreparticular description of the disclosure briefly described above will berendered by reference to specific embodiments thereof which areillustrated in the appended drawings. Understanding that these drawingsdepict only typical embodiments of the disclosure and are therefore notto be considered limiting of its scope, the disclosure will be describedwith additional specificity and detail through the use of theaccompanying drawings in which:

FIG. 1 is an image depicting nano- and micro-particles (NMP) with aprimary proppant.

FIG. 2 depicts the nano- and micro-particles (NMP).

FIG. 3 is a graph depicting the size distribution of nano- andmicro-particles (NMP).

DETAILED DESCRIPTION

The particulars shown herein are by way of example and for purposes ofillustrative discussion of the preferred embodiments of the presentdisclosure only and are presented in the cause of providing what isbelieved to be the most useful and readily understood description of theprinciples and conceptual aspects of various embodiments of thedisclosure. In this regard, no attempt is made to show structuraldetails of the disclosure in more detail than is necessary for thefundamental understanding of the disclosure, the description taken withthe drawings making apparent to those skilled in the art how the severalforms of the disclosure may be embodied in practice.

The following definitions and explanations are meant and intended to becontrolling in any future construction unless clearly and unambiguouslymodified in the following examples or when application of the meaningrenders any construction meaningless or essentially meaningless. Incases where the construction of the term would render it meaningless oressentially meaningless, the definition should be taken from Webster'sDictionary 3^(rd) Edition.

Nano- and micro-particles (NMP) can be utilized as proppants to enhancethe conductivity of microfractures and fluid-loss-control additives forhydraulic fracturing operations. In an embodiment, nano-, micro-, or amixture of nano- and micro-particles can be used.

In an embodiment, the NMP are made from an oil/water emulsion. In anembodiment, the emulsion is made by mixing a liquid solvent, at leastone surfactant, a particle-forming compound, and at least one curingagent together. The particle-forming compound and the curing agents aremixed together to form the oil phase in the oil/water emulsion. Aftercuring, the “oil” droplets turn into NMP.

In an embodiment, the liquid solvent comprises water, seawater, brinecontaining monovalent, divalent, and multivalent salts, an alcohol suchas ethanol, propanol, butanol, or combinations thereof.

In an embodiment, the surfactant comprises anionic surfactants, cationicsurfactants, nonionic surfactants, amphoteric surfactants orcombinations thereof.

In an embodiment, the particle-forming compound can be but is notlimited to aliphatic epoxides, anhydrides, glycidyl amine epoxide,cycloaliphatic epoxides, epoxy functional resins, polyurethane resins,phenol-formaldehyde resin, bis-phenol A diglycidyl ether, poly glycidylethers, acrylic resin, glycidyl ethers, bis-phenol F diglycidylethernovalac resins, or combinations thereof.

In an embodiment, the curing agent can be but is not limited toisophorone diamine, boron tri-fluoride derivatives, imidazolines,mercaptans, hydrazides, polyamides, functional resins, mono ethanolamine, benzyl dimethylamine, lewis acids, tertiary amines,cycloaliphatic amines, amidoamines, aliphatic amines, aromatic amines,isophorone, imidazoles, sulfide, amides, and their derivatives.

If desired, acid or alkali pH control agents can be added to the liquidsolvent. In an embodiment, the pH control agents can be selected frombut not limited to mineral acids such as hydrochloric acid, sulfuricacid, nitric acid, and fluoroboric acid, sulfonic acids such asethanesulfonic acid and methanesulfonic acid, carboxylic acids such asacetic acid, sodium hydroxide, potassium hydroxide, calcium hydroxide,and combinations thereof.

If desired, viscosity enhancers can be added to the liquid solvent. Inan embodiment, the viscosity enhancers can be selected from but notlimited to nanoparticles such as calcium carbonate nanoparticles andsilicate nanoparticles, and water-soluble polymers such aspolyacrylamide and polyvinyl alcohol.

In an embodiment, NMP are formed by mixing the liquid solvent, at leastone surfactant, a particle-forming compound, and at least one curingagent together for 3-15 minutes to form an oil/water emulsion and thenallowed to stand undisturbed in water bath at 30-150° C. for 5-200minutes. In an embodiment, they are mixed together for about 10 minutes.In an embodiment, the temperature is 60° C. In an embodiment, theemulsion is allowed to stand in the water bath for 60 minutes. In anembodiment, seawater is used as liquid solvent. In an embodiment, alkaliis added to adjust the pH. In an embodiment, the pH is adjusted to atleast about 12. This method results in formation of particles across abroad size range from nanoscale to microscale.

The NMP serve multiple functions in hydraulic fracturing operations. Inan embodiment, NMP can be added to the pad and/or fracturing fluids toincrease the conductivity of nano- and micro-fractures. In anembodiment, NMP are used to complement a primary proppant functioning tokeep the main fractures open, as depicted in FIG. 1. In an embodiment,NMP additionally function as a fluid-loss-control additive.

The density of the nanoparticles (diameter <1 μm) and microparticles(diameter <250 μm) made through the disclosed method is no more than1.50 g/ml and thus far lower than nano- and micro-particle proppantsdescribed in the prior art, for example, silica flour and ceramicmicroparticle proppants and silicon oxide, calcium oxide, and aluminumoxide nanoparticles produced from fly ash. The low density permits NMPto be transported far in the hydraulic fracture with low settling rate.

In addition, NMP are deformable. This prevents the NMP from beingcrushed when fractures attempt to close after the injection has stoppedand enhances flushing of NMP out of nano- and micro-fractures.

EXAMPLES Example 1

The liquid for making the oil/water emulsion to form the NMP is shown inTable 1. The liquid was mixed for 10 minutes to form an emulsion andthen allowed to stand undisturbed in water bath at 60° C. for 1 hour toreact to form NMP. The NMP formed are shown in FIG. 2. The particle sizedistribution was determined by Mastersizer 3000 laser particle sizeanalyzer. The size distribution results are shown in FIG. 3.Microparticles were formed having sizes ranging from a diameter of 1 μmto ≤250 μm. Nanoparticles were formed having sizes of a diameter of <1μm).

Liquid components Wt. % Tween ™ 20 3 Hostafrac SF14413 7 Seawater 29 pHcontrol agent 1 Max CLR ™ A 30 Max CLR ™ B 30

Tween™ is a registered trademark of Croda International plc, containingAlkoxylate.

Hostafrac SF14413 is a product of Clariant Corporation. 10-20% by weightproprietary ingredient 6615, 10-20% by weight ethoxylated isotridecanol,1-10% proprietary ingredient 6715, 1-5% solvent naphtha, 0.1-1% byweight naphthalene.

Max CLR™ is a trademark of Polymer Composites Corporation.

Max CLR™ A is a modified bisphenol A epoxy resin, 90-100% by weightphenol, 4-(1-methylethylidene) Bis, Polymer with (Chloromethane)Oxerane, 1-5% by weight epoxidize diluent reactive, 0-10% by weightepoxidize cresylglyciderether modified, and 0.1-0.5% by weightnon-silicone additive.

Max CLR™ B is an amine modified curing agent. It contains about between5-15% by weight benzyl alcohol, 15-35% by weight isophoromediamineadduct, and 50-60% by weight aliphatic amine adduct.

All of the compositions and methods disclosed and claimed herein can bemade and executed without undue experimentation in light of the presentdisclosure. While the compositions and methods of this disclosure havebeen described in terms of preferred embodiments, it will be apparent tothose of skill in the art that variations may be applied to thecompositions and methods and in the steps or in the sequence of steps ofthe methods described herein without departing from the concept, spiritand scope of the disclosure. More specifically, it will be apparent thatcertain agents which are both chemically related may be substituted forthe agents described herein while the same or similar results would beachieved. All such similar substitutes and modifications apparent tothose skilled in the art are deemed to be within the spirit, scope andconcept of the disclosure as defined by the appended claims.

1. A method for producing a mixture of nano- and micro-particles for useas a proppant and fluid-loss-control additive, comprising: mixing aliquid solvent, at least one surfactant, a particle-forming compound, atleast one curing agent to form an emulsion, and at least one pH controlagent that elevates the pH of the emulsion to at least about 12; andincubating the emulsion to permit formation of nano- andmicro-particles; wherein the diameters of the nano- and micro-particlesare under 1 μm for the nano-particles and a range of 1 to 250 μm for themicro-particles.
 2. The method of claim 1 wherein the emulsion isincubated at about 30-150° C.
 3. The method of claim 1 wherein theemulsion is incubated for about 5-200 minutes.
 4. The method of claim 1,wherein the liquid solvent comprises water, seawater, brine comprisingmonovalent, divalent, and multivalent salts, an alcohol comprisingethanol, propanol, butanol, or combinations thereof.
 5. The method ofclaim 1, wherein the at least one surfactant comprises anionicsurfactants, cationic surfactants, nonionic surfactants, amphotericsurfactants or combinations thereof.
 6. The method of claim 1, whereinthe particle-forming compound comprises aliphatic epoxides, anhydrides,glycidyl amine epoxide, cycloaliphatic epoxides, epoxy functionalresins, polyurethane resins, phenol-formaldehyde resin, bis-phenol Adiglycidyl ether, poly glycidyl ethers, acrylic resin, glycidyl ethers,bis-phenol F diglycidyl ethernovalac resins, or combinations thereof. 7.The method of claim 1, wherein the at least one curing agent comprisesisophorone diamine, boron tri-fluoride derivatives, imidazolines,mercaptans, hydrazides, polyamides, functional resins, mono ethanolamine, benzyl dimethylamine, lewis acids, tertiary amines,cycloaliphatic amines, amidoamines, aliphatic amines, aromatic amines,isophorone, imidazoles, sulfide, amides or their derivatives. 8.(canceled)
 9. The method of claim 1, wherein the pH control agentcomprises sodium hydroxide, potassium hydroxide, or combinationsthereof.
 10. (canceled)
 11. The method of claim 1, further comprisingadding a viscosity enhancer to the emulsion.
 12. The method of claim 11,wherein the viscosity enhancer comprises calcium carbonatenanoparticles, silicate nanoparticles, or water-soluble polymerscomprising polyacrylamide or polyvinyl alcohol.
 13. A nano- andmicro-particle mixture comprising: a liquid solvent, at least onesurfactant, a particle-forming compound, a pH control agent, and atleast one curing agent to form an emulsion; wherein the size of the nanoparticles is less than 1 μm and the size of the microparticles isbetween 1 and 250 μm; and wherein the pH of the emulsion is at leastabout
 12. 14. The mixture of claim 13 wherein the emulsion is incubatedat about 60° C. and for about 60 minutes.
 15. The mixture of claim 13,wherein the liquid solvent comprises water, seawater, brine comprisingmonovalent, divalent, and multivalent salts, an alcohol comprisingethanol, propanol, butanol, or combinations thereof; the at least onesurfactant comprises anionic surfactants, cationic surfactants, nonionicsurfactants, amphoteric surfactants or combinations thereof; theparticle-forming compound comprises aliphatic epoxides, anhydrides,glycidyl amine epoxide, cycloaliphatic epoxides, epoxy functionalresins, polyurethane resins, phenol-formaldehyde resin, bis-phenol Adiglycidyl ether, poly glycidyl ethers, acrylic resin, glycidyl ethers,bis-phenol F diglycidyl ethernovalac resins, or combinations thereof;and the at least one curing agent comprises isophorone diamine, borontri-fluoride derivatives, imidazolines, mercaptans, hydrazides,polyamides, functional resins, mono ethanol amine, benzyl dimethylamine,lewis acids, tertiary amines, cycloaliphatic amines, amidoamines,aliphatic amines, aromatic amines, isophorone, imidazoles, sulfide,amides or their derivatives.
 16. The mixture of claim 13, wherein the pHcontrol agent comprises sodium hydroxide, potassium hydroxide, calciumhydroxide, or combinations thereof.
 17. The mixture of claim 13, furthercomprising a viscosity enhancer to the emulsion; wherein the viscosityenhancer comprises calcium carbonate nanoparticles, silicatenanoparticles, or water-soluble polymers comprising polyacrylamide orpolyvinyl alcohol.
 18. (canceled)
 19. The mixture of claim 13 whereinthe density of the nanoparticles and microparticles is 1.50 g/ml orless.
 20. A method of using the nano- and micro-particle mixtureproduced from the method of claim 1 to increase the conductivity ofmicrofractures comprising adding the mixture to a pad or fracturingfluids. The method of claim 1 wherein the resulting mixture is added toa pad or fracturing fluids in order to increase the conductivity ofmicrofracture and to reduce fluid loss.